1. Field of the Invention
The present invention generally relates to a filtering apparatus of the type utilizing elongated baglike tubular filters for filtering particulate material carried in a gas or liquid stream in a filter housing and, more particularly, to an integrated molded collar, filter bag, cage and locking ring assembly for use in baghouses.
2. Description of the Related Art
A filtering apparatus of the type related to the present invention generally includes multiple tubular filter bags mounted in a filter housing or baghouse with each filter bag having a supporting frame or cage positioned therein to hold the filter bag in an open, hollow tubular configuration. The bags are open at an outlet end and closed at their other end. Particulate-laden gas or liquid is directed into the baghouse and through the gas-permeable filter bags. The particulate material is filtered and retained on the exterior surface of the filter bags while the filtered gas or liquid passes through the filter bag. Periodically, a reverse purge of gas or fluid is directed into the open outlet end of the filter bags for dislodging any trapped particulate material from the bags and thus, cleaning the filter bags.
Typically, a filter bag can have a useful life of up to about two years. However, in some filtering applications, the inability to effectively clean the filter bags is so severe that it is necessary to frequently replace the filter bags. Under extreme conditions, such as when the particulate material is of a highly abrasive nature, the filter bags may wear out in a matter of weeks. Thus, the ability to readily remove and replace the filter bags is important.
A common method of locking filter bags in place in the baghouse is by using clamps, locking-strips and similar devices which require special equipment for fastening or unlocking. The locking devices also are generally unwieldy and increase the cost of the filter bag assembly. A typical baghouse may contain hundreds of filter bags. Thus, a large number of such locking devices can be required, and replacement of the filter bags becomes time consuming and costly.
Conventional fastening devices often exhibit sharp edges or wear points which cause breakage or excessive wear of the filter bags with prolonged use. Such fastening devices combined with exposure to vibrations damages the filter bags. In addition, protruding locking devices render cleaning more difficult and cause accidents.
Accordingly, a need has arisen to eliminate the abovenoted drawbacks associated with conventional locking devices, as well as to provide a filter assembly which is easy and inexpensive to install.
Some attempts have been made in the art to overcome such drawbacks. For instance, FIG. 1 shows a cross-sectional view of a conventional double-beaded snap band filter bag and cage assembly for use in baghouses. This conventional filter bag and cage assembly sought to overcome some of the drawbacks associated with the complex locking devices discussed above. However, in so doing, this conventional arrangement has introduced further problems with respect to installation and removal.
In FIG. 1, reference number 100 represents a filter bag assembly for use in a baghouse (not shown). The baghouse includes a cell plate 110, with one of a plurality of generally circular openings 190 shown. The filter bag assembly 100 includes a double-beaded snap band assembly 120 secured at points 135 to the filter bag 140. The filter bag 140 is supported by a cage assembly 150. The cage assembly 150 includes an upper portion 155 that loosely overlaps the double-beaded snap band assembly 120.
The double-beaded snap band assembly 120 includes an upper bead 122 and a lower bead 124. The beads 122 and 124 are generally double beads of felt tape, fiberglass rope or fabric filling. These beads overlap the cell plate 110 around the opening 190. The beads 122 and 124 are adhesively secured to a metal snap band 126. The metal snap band 126 is typically made of stainless steel, or other suitable material, and provides leverage for the seal by applying a radially outward force. The entire double-beaded snap band assembly 120 is covered with a fabric or gasket cuff 128. The cuff 128 is secured to the filter bag at points 135.
The conventional filter bag and cage assembly shown in FIG. 1 has several disadvantages. It is difficult and time consuming to install and is costly to manufacture. Moreover, because the bottom bead 124 lies underneath the cell plate 110, it is extremely difficult to remove the filter assembly 100 from the cell plate 110 without destroying the reusable cage, and practically impossible to remove the filter assembly into the clean, outlet end above the cell plate 110.
To install the conventional filter bag and cage assembly 100 shown in FIG. 1, it is necessary first to compress the metal band 126 into a bone-shape. The filter assembly 100 is then dropped into position through the opening 190 in the cell plate 110, and the snap band assembly 120 is released with a snap-action to seat the fabric cuff 128 in the groove between the beads. This snap-action can pinch fingers and is dangerous to the installer. The cage assembly 150 is then dropped into place within the bag. The upper portion 155 of the cage assembly 150 is placed over the filter assembly 100 for protection.
For removal of the filter assembly 100, it is necessary to first remove the cage assembly 150. Then, it is necessary to once again compress the metal snap band 126 into the bone-shape. The filter assembly 100 is then pushed through the cell plate 110 into the dirty area of the baghouse. Such an operation adds cost and time to the removal procedure. Moreover, that operation is undesirable, because it is preferred to remove the bag into the clean, outlet end of the baghouse. In addition, the filter bag 140 often sticks to the cage assembly 150 after use. When sticking occurs, the filter bag and/or the cage must be destroyed for removal of the filter bag assembly 100. This, again, increases costs.
Attempts have been made to eliminate the drawbacks noted above with respect to the double-beaded snap band assembly. For instance, U.S. Pat. No. 4,014,672 discloses a gas filter tube locking apparatus that eliminates both the upper bead from the bag and the overlapping upper portion of the cage assembly in the typical double beaded snap band assembly. However, the gas filter tube locking apparatus in the '672 patent includes the undesirable lower bead that prevents removal of the bag assembly into the clean, outlet end of the baghouse.
The gas filter tube locking apparatus of the '672 patent includes a bag filter attached to a socket. The socket is on the outer extremity of a self-expanding thickening portion. The socket is attached to a semi-annular bulge that constitutes the lower bead. The lower bead contacts the bottom of a cell plate. A collar partially extending over the cell plate holds the gas filter tube in place. However the lower bead in the apparatus of the '672 patent presents the same difficulties in removal as the double-beaded snap band assembly discussed above, i.e., the lower bead prevents upward removal. Accordingly, the expensive and time consuming removal associated with the double beaded snap band assembly has not been overcome by the '672patent.
Moreover, no gasketing is provided between the collar and the cell plate of the filtering device in the '672patent. This can create leaks, should the lower bead fail in any respect, for example, caused by workmen walking on the device, as often occurs.
The locking cylinder and the bag filter in the '672 patent are made of different materials. This increases manufacturing costs. Moreover, the external diameter of the locking cylinder is chosen so that the cylinder can slide into the socket containing the bag filter without damaging the filter, but without much clearance. This requires a very sensitive and time consuming installation. If extreme care is not taken, the bag filter can readily be damaged. This, too, is a severe disadvantage.
Accordingly, a need has arisen to overcome the drawbacks discussed above, and to provide an improved filter assembly for bag houses.